One of the methods currently used for refuelling operations or transferring fuel comprises a telescoping tube, which in turn comprises a fixed part and a moving part, this moving part being capable of being extended telescopically with respect to the fixed part, carrying out the transfer of fuel from one tank to another in this manner. This telescoping tube usually comprises a system for extending and retracting its fixed part with respect to the moving part, such that the aforementioned telescoping extension and retraction can be achieved and enabling it to be stopped at nominal positions without reaching limits at which impact occurs. On certain occasions, when the aforementioned extension and retraction system fails, it is necessary for the moving part to be capable of locking against the fixed part, the former cushioning the impact that this action involves, so as to prevent the failure of the refuelling system.
On the other hand, given that there will be a transfer of fuel in the extended tube, between its fixed and moving parts, it is necessary that the sealing of the moving part relative to the fixed part is correct and that there are no fuel leaks. There is, therefore, the need for an effective dynamic seal.
Furthermore, and given that what is transferred is highly inflammable fuel, the telescoping tube needs to be perfectly designed to protect it during operation from possible electrical discharges or electric arcs due, for example, to lightning strikes or to the accumulation of electrostatic charge due to different types of friction which can occur in certain fuel transfer operations.
One of the methods currently used for in-flight refuelling operations for an aircraft is based on the use of an arm or mast device known as a boom, which comprises a telescoping tube with a fixed part and a moving part as described above, it being possible for this moving part to extend telescopically with respect to the fixed part, carrying out the transfer of fuel from the tanker aeroplane to the receiving aeroplane in this way. The aforementioned boom is in turn connected to the tanker aeroplane by means of an articulated system.
A specific system is known, from U.S. Ser. No. 11/411,984 from the same applicant, for protection against electrical discharges of an aircraft telescoping tube for in-flight refuelling. The aforementioned system comprises insulating media and low conductivity media to reduce the current from lightning strikes and to discharge the static charge created during refuelling, in addition to conducting media to provide a safe path for lightning currents and good earthing for the electrostatic charge. The aforementioned system is specifically for protection against electrical discharges.
Also known, from US document 2007/0257154, is a system to protect against electrical discharges, particularly those from lightning striking an aircraft during in-flight refuelling operations between a tanker aeroplane and a receiving aeroplane. This system is based on injecting an inert gas into the zone adjoining the refuelling zone such that the fuel which may escape to the outside does not ignite in the case of a lightning strike on either of the two aircraft. The aforementioned system is also specifically for protection against electrical discharges.
Also known, on the other hand, are cushioning, separation and sealing systems for an aircraft telescoping tube for carrying out in-flight refuelling operations, such as those described in U.S. Pat. No. 4,540,144, for example. Described in this document is a telescoping tube which performs in-flight refuelling operations, which comprises a system for the extension and retraction of the tube, together with a housing to separate this system from the exterior, the system also comprising means for blocking the telescoping tube in its retracted position. Such a system does not comprise specific means for protection against electrical discharges.
Hence, the integration of elements or means for performing the aforementioned actions of dynamic sealing, cushioning and protection against electrical discharges are usually carried out by integrating different units to perform the aforementioned actions into the moving part of the telescoping tube, involving an increase in the weight and length of the moving part and, consequently, of the telescoping tube as a whole, with this increase compromising the functions and dimensions of this telescoping tube.
As such, the purpose of this invention is to resolve the aforementioned problems.